Generally, methods for driving an LCD can be classified into two methods, the color filter method and the field-sequential driving method, based on methods of displaying color images.
The color filter method divides a pixel into three sub-pixels that corresponds to red resist, green resist and blue resist respectively to compose a color. The color sequential method sequentially switches three primary colors within the time humans do not perceive the flicker of the image to compose a color. That is, the primary colors are sequentially displayed in three time segments. Therefore, a complete color image is displayed as a rapidly changing sequence of primary monochrome images. Since every pixel unit in the display contributes to every primary image, a color sequential imaging display must address the pixel units first to select required pixel units to display.
Typically, since three primary colors are sequentially switched in three time segments in the color sequential method, liquid crystal molecules have to be rotated from the prior primary color to the present primary color. Therefore, the rotated angle of the prior primary color influences the rotated angle of the present primary color. For example, when two pixels with different primary colors in the prior frame are changed to the same primary color in the present frame, a color difference exists in the two pixels since the liquid crystal molecules in the two pixels are rotated from different start angles. This can reduce the display quality.
To resolve the foregoing problem, black data is first written into each pixel to reset the liquid crystal molecules to confirm the liquid crystal molecules in each pixel are rotated from the same start angle. FIG. 1 illustrates the driving scheme. A frame is separated to three sub-frames, including red sub-frame (R-SF), green sub-frame (G-SF) and blue sub-frame (B-SF) to sequentially show three primary colors, red, green and blue, in the persistence of vision time. The three primary colors within the time that humans do not perceive the flicker of image to compose a color. Each sub-frame of the drive scheme has four intervals. During the first interval 101 black data is written into each pixel to reset the liquid crystal molecules. In the second interval 102 addresses are assigned to the pixels for writing color data into pixels. The third interval 103 is the response time of the liquid crystal molecules. During the fourth interval 104 the corresponding backlight is turned on based on the corresponding color data. The fourth interval 104 is the critical interval. When the fourth interval 104 is too short to completely turn on the backlight, the brightness of the panel is reduced, which will influence the panel quality.
Therefore, it is the objective for a designer to lengthen the fourth interval to increase the brightness to improve the quality